The thing is, they hijack the IDEAS but they don’t hijack the way the idea has been presented. If they do so, it’s called plagiarism and it’s illegal.
What they do is use the idea that someone else had and then spin that idea into something else that is uniquely theirs and that is often unrecognizable as the original idea. This makes perfect sense because that original idea has usually changed so much that by the time it’s presented to the public it actually is a new idea entirely.
Because one way creativity grows is by rubbing against other creativity and the greater the friction the greater the creativity.